Combined hydrotreating and process

ABSTRACT

First ( 210 ) and second ( 240 ) feedstocks are hydrotreated in an integrated hydrogenation plant ( 200 ) using a hot separator ( 230 ) that provides a vapor stream containing at least some of the hydrotreated first feedstock ( 210 ), wherein the second feedstock ( 240 ) is mixed with the vapor stream at a position downstream of the separator ( 240 ) and upstream of the a second hydrotreating ( 250 ) reactor to form a mixed second feedstock that is fed into the second hydrotreating reactor ( 250 ) to produce a ultra-low sulfur product.

FIELD OF THE INVENTION

[0001] The field of the invention is petrochemistry, and particularlyhydrotreating of diesel and fluid catalytic cracking gas oil feedstocks.

BACKGROUND OF THE INVENTION

[0002] Hydrotreating is a commonly used process in many modernrefineries, in which hydrogen is contacted in the presence of a catalystwith a hydrocarbonaceous feedstock to remove impurities, includingoxygen, nitrogen, sulfur, and unsaturated hydrocarbons. Consequently,hydrotreating is frequently employed to reduce the sulfur content fromrefined intermediates and is also commonly referred to ashydrodesulfurization. Hydrodesulfurization is typically used within arefinery in combination with processes including feed pretreatment ofcatalytic reformers, catalytic crackers, and hydrocrackers, productquality improvement for naphtha, diesel, jet, heating oil and residues,saturation of olefins, and polycyclic aromatics. There are numeroushydrotreating configurations and processes known in the art, andcontinuous efforts to reduce energy and material consumption led tointegration of hydrotreating reactors in various processes.

[0003] For example, in one integration concept, a hydrotreater iscombined with a hydrocracker as disclosed in U.S. Pat. No. 3,328,290 toHengstebeck that describes a two-stage hydrocracking process whereinfresh feed is combined with effluent from the hydrocracking stage andthe combined streams are then introduced into a hydrotreating stage. Ahigher-boiling fraction is then separated from the hydrotreater effluentand fractionated to produce a light product and a heavier-bottomsstream, which is then recycled with hydrogen-containing gas back to thehydrocracking stage.

[0004] Another example U.S. Pat. No. 6,235,190 to Bertram describes anintegrated hydrotreating and hydrocracking process in which twohydrotreating catalysts of different activity are operated in series toprovide improved products that are then subjected to a hydrocrackingprocess to convert the hydrotreated effluent to lighter products with areduced aromatic hydrocarbon content.

[0005] In a further example, as described in U.S. Pat. No. 6 combinedhydrotreating/hydrocracking process is described in which ahydrocracking stage is followed by a hydrodewaxing stage with a singlefeed and a bottoms fraction recycle to produce a naphtha product, adistillate boiling above the naphtha range, and a lubricant.

[0006] In yet another system, as described in U.S. Pat. No. 6,328,879 toKalnes, two independent feedstocks are hydrocracked in a catalytichydrocracking process that employs a hydrocracking zone, a hydrotreatingzone, and a high pressure product stripper to produce various productsfrom two feedstocks, wherein the products have a lower boiling pointrange than the feedstocks.

[0007] Alternatively, more than one hydrotreater reactor, and orcatalyst beds may be employed for catalytic hydrogenation as describedin U.S. Pat. No. 3,537,981 to Parker, or U.S. Pat. No. 6,103,105 toCooper. While Parker's process employs a first hydrotreating reactorcoupled to a separator that is in series with a second hydrotreatingreactor, Cooper et al. employ two serially connected hydrotreatingcatalyst beds without the use of a separator. However, both Coopers andParkers configuration are typically limited to only a single feedstock.Alternatively, as described in U.S. Pat. No. 5,958,218 to Hunter, twohydrocarbon feedstocks are hydrotreated in parallel while hydrogen flowsin series between the reactors. While Hunters configuration allowshydrotreating of two at least somewhat different feedstocks, thecatalytic reactors will generally operate at different hydrogen partialpressures. Consequently, the balance of the feedstocks will have to beproperly balanced with the particular hydrogen partial pressures toyield the desired products.

[0008] Thus, although many integrated processes have provided at leastsome advantage over other known configurations and methods, suchconfigurations and methods are frequently limited to processes involvinghydrocracking, or hydrotreating of a single boiling range (e.g.,naphtha, diesel, gasoil, resid) feedstock. Consequently, all or almostall of the known hydrotreating processes require separate plants wheremore than one feedstock is employed. Therefore, there is still a need toprovide improved configurations and methods for hydrotreating ofpetroleum products.

SUMMARY OF THE INVENTION

[0009] The present invention is directed to configurations and methodsfor hydrotreating plants, and especially for integrated hydrotreatingplants in which at least two feedstocks with different boiling pointranges (e.g., gas oil and diesel oil) are hydrogenated.

[0010] In one aspect of the inventive subject matter, contemplatedplants include a first hydrotreating reactor that receives a firstfeedstock and produces a hydrotreated first feedstock and furtherinclude a hot separator that receives the hydrotreated first feedstockand produces a hot hydrotreated liquid and a hot hydrotreated vapor thatcontains at least a portion of the hydrotreated first feedstock. Atleast a portion of the hot hydrotreated vapor is mixed with a secondfeedstock to form a mixed second feedstock that is fed into a secondhydrotreating reactor to form a product, wherein the second feedstockhas a boiling point range that is lower than the first feedstock. Thisconfiguration is especially applicable where the sulfur content of theproduct of the second hydrotreating reactor must be maintained at a verylow level.

[0011] In a further contemplated aspect, a gas oil first feedstock anddiesel oil second feedstock are considered especially advantageous,especially where the charge rate of the first feedstock and the secondfeedstock have a ratio of between about 1:1 to about 1:2. Whereappropriate, first and/or second hydrotreating reactors may furtherreceive a hydrogen-containing stream, some or all of which may berecycled in the plant from an effluent of the second hydrotreatingreactor or may be a makeup hydrogen stream. Furthermore, it iscontemplated that configurations according to the inventive subjectmatter may be realized in a new plant. However, the hot separator andthe second hydrotreating reactor may also be integrated as an upgradeinto an existing hydrotreating plant.

[0012] Consequently, a method of hydrotreating may comprise a step inwhich a first feedstock is hydrotreated in a first hydrotreating reactorto produce a hydrotreated first feedstock. In another step, thehydrotreated first feedstock is fed into a hot separator that produces ahot hydrotreated liquid and a hot hydrotreated vapor that contains atleast a portion of the hydrotreated first feedstock, and in yet anotherstep, at least a portion of the hot hydrotreated vapor is mixed with asecond feedstock to form a mixed second feedstock. In a still furtherstep, the mixed second feedstock is fed into a second hydrotreatingreactor to form a product.

BRIEF DESCRIPTION OF THE DRAWING

[0013]FIG. 1 is a schematic view of an exemplary configuration of aprior art hydrotreating plant.

[0014]FIG. 2 is a schematic view of an exemplary configuration of ahydrotreating plant according to the inventive subject matter.

DETAILED DESCRIPTION

[0015] Various known configurations and processes for desulfurationand/or denitrification using hydrotreating of a feedstock employ ahydrotreating reactor in which a hydrocarbonaceous feed is reacted withhydrogen in the presence of a catalyst to form H₂S and/or NH₃ fromsulfur- and/or nitrogen-containing compounds in the feed. Prior art FIG.1 depicts a typical configuration 100 for such plants. Here, a singlefeedstock (e.g., diesel) 110 is passed through a heater 120 andsubsequently fed into a hydrotreating reactor 130. Hydrogen (separately[via line 141], or in combination [via line 142] with the feedstock) isadded to the catalyst in the hydrotreating reactor and the hydrotreatedproduct 112 is (after a cooling step in cooler 180) separated inseparator 150 into a gaseous portion 112A, which predominantly compriseshydrogen and hydrogen sulfide, and a liquid portion 112B, whichcomprises hydrotreated gas oil, wild naphtha, and remaining sour gas.The hydrogen from the gaseous portion is typically purified in anabsorber 152 with an amine-containing solvent, and recycled (supra) intothe hydrogen reactor via compressor 160. The hydrotreated feed 112C canthen be retrieved from column 170 along with wild naphtha 112D and sourgas 112E. While such configurations work relatively well for a singletype of feedstock (e.g., gas oil, diesel, etc.), known plants withmultiple feedstocks (e.g., gas oil and diesel) generally requiremultiple and separate hydrotreating configurations, which addsignificant cost to construction and operation of such plants.

[0016] In their efforts to improve configurations and methods forhydrotreating hydrocarbonaceous feeds, the inventors have discoveredthat multiple types of feedstock (i.e., feedstocks with differentboiling point ranges—e.g., gas oil and diesel) can be hydrotreated in anintegrated configuration, in which a hot separator is fluidly couple(hydrotreating reactor, and in which a single hydrogen recycl cooler orheat exchanger, a liquid/gas separator, an amine scrubber, and acompressor) can be employed for both hydrogen reactors.

[0017] Thus, in a particularly preferred aspect of the inventive subjectmatter, a plant comprises a first hydrotreating reactor that receives afirst feedstock and produces a hydrotreated first feedstock and a hotseparator that receives the hydrotreated first feedstock and produces ahot hydrotreated liquid and a hot hydrotreated vapor that contains atleast a portion of the hydrotreated first feedstock, wherein at least aportion of the hot hydrotreated vapor is mixed (preferably at a positiondownstream of the separator and upstream of the second hydrotreater)with a second feedstock to form a mixed second feedstock that is fedinto a second hydrotreating reactor to form a product, and wherein thesecond feedstock has a boiling point range that is lower than the firstfeedstock. In further contemplated aspects, the separator, the firsthydrotreating reactor, and the second hydrotreating reactor are operatedsuch that the product has a sulfur content of less than 100, morepreferably less than 50, and most preferably less than 15 ppm.

[0018]FIG. 2 depicts an exemplary configuration of a hydrotreating plant200, in which two different hydrocarbonaceous feedstocks arehydrotreated using an integrated configuration with a single hydrogenrecycle loop. Here, first feedstock 210 (e.g., gas oil ) is heatexchanged against the hydrotreated first feedstock 210′ and furtherheated in heater 202A before introduction into the first hydrotreatingreactor 220. The hydrotreated first feedstock 210′ is then fed into hotseparator 230 that is operated under conditions to separate hydrotreatedfirst feedstock 210′ into hot hydrotreated liquid 210′L and hothydrotreated vapor 210′V, wherein the hot hydrotreated vapor 210′Vcontains at least a portion of the hydrotreated first feedstock 210′.The hot hydrotreated vapor 210′V is then mixed with the second feedstock240 (e.g., diesel feed) to form a mixed second feedstock 240′ that isfed (after heat exchange against product 260 and further heating inheater 202B) into the second hydrotreating reactor 250. The secondhydrotreating reactor 250 produces product 260. A downstream separator270 recovers at least a portion of the hydrogen from the product 260,and the recovered hydrogen is fed into a hydrogen recycle loop 280(including cold separator 282 and absorber 284) that eventually providesat least part of the hyd separator via compressor 290. Thus, it shouldbe recognized that in contemplated configurations, the hot separator isoperated such that at least separated from the hydrotreated feedstockand fed into the hydrotreating reactor in which the second feedstock ishydrotreated.

[0019] It should be especially appreciated that the terms “hydrotreatingreactor” and “hydrocracking reactor” are not referring to the same typeof reactor. As used herein, the term “hydrotreating reactor” refers to areactor in which a hydrocarbon-containing feed is reacted with hydrogenin the presence of a catalyst under conditions that (a) result in lessthan 15% conversion, and more typically less than 10% conversion, and(b) result in the formation of H₂S and/or NH₃ from sulfur- andnitrogen-containing compounds in the hydrocarbon-containing feed. Incontrast, the term “hydrocracking reactor” as used herein refers to areactor in which a hydrocarbon-containing feed is converted to lighterproducts (i.e., the average molecular weight decreases), wherein theterm “conversion” or “converted” means that a particular percentage offresh feed changes to middle distillate, gasoline and lighter products(see e.g., “Hydrocracking Science And Technology” by J. Scherzer and A.J. Gruia; Marcel Decker, Inc.). Thus, contemplated hydrocrackingreactors will have a conversion of at least 15%, more typically at least30%, and most typically at least 50%.

[0020] As also used herein, the term “hot separator” refers to aseparator that is fluidly coupled to at least two hydrotreating reactorssuch that the hot separator receives an at least partially hydrotreated(or otherwise at least partially purified) first feedstock at atemperature of about 400° F. and higher, and wherein the hot separatorproduces a hot hydrotreated vapor that (a) contains at least a portionof the first feedstock and (b) is feed into a second hydrotreatingreactor.

[0021] With respect to the first and second feedstocks (210 and 240,respectively) it should be appreciated that various hydrocarbonaceousfeedstocks are considered suitable for use herein, and in especiallycontemplated aspects the first hydrocarbonaceous feedstock comprises gasoil and the second hydrocarbonaceous feedstock comprises diesel. In astill further especially contemplated aspect, the secondhydrocarbonaceous feedstock may also comprise cycle oil from an upstreamFCC (fluid catalytic cracking) reactor. However, in alternative aspects,suitable hydrocarbonaceous feedstocks also include crude or partiallypurified petroleum fractions, including light gas oil, heavy gas oil, sdeasphalted oil, kerosene, jet fuel, etc. Furthermore, it is ge andsecond hydrocarbonaceous feedstocks have different boiling point ranges,wherein the first hydrocarbonaceous feedstock typically has a boilingpoint range that is higher (at least 5 degrees centigrade, moretypically at least 10 degrees centigrade, and most typically at least 25degrees centigrade as measured from the initial boiling point in theboiling point range) than the second boiling point range.

[0022] Contemplated hot separators are preferably operated underconditions that will allow separation of the hydrotreated firstfeedstock into a liquid portion and a vapor portion, wherein the vaporportion comprises at least a part of the hydrotreated first feedstock.Thus, it is generally preferred that contemplated hot separators willreceive hydrotreated first feedstock that is not, or only partiallycooled (e.g., by heat exchange with first feedstock). Consequently, itshould be appreciated that suitable operation temperatures forcontemplated hot separators are generally above 300° F., more typicallyabove 400° F., and most typically in a range between about 450° F. and550° F.

[0023] Furthermore, it is contemplated that appropriate hot separatorswill be operated at a pressure that is at or close to the pressure inthe first hydrotreating reactor and at a pressure that is at or abovethe pressure of the second hydrotreating reactor. Consequently, suitablehot separators will typically be operated at between about 1000-2500psi, and more typically at a pressure of about 1200 psi and about 2400psi. However, where suitable it should be appreciated that the pressuremay also be less than 1000 psi and especially contemplated lowerpressures are generally between 1000 to 400 psi, and even less.Similarly, where hydrotreating conditions allow, hot separators may alsobe operated at a pressure above 2500 psi, and suitable higher pressuresinclude pressures between 2500 to 4000 psi, and even higher.

[0024] With respect to the vapor comprising at least a portion of thehydrotreated first feedstock, it should be recognized the vapor willinclude significant quantities (i.e., at least 20 mol %, more typicallyat least 35 mol %) of hydrogen that has not reacted with components ofthe first feedstock in the first hydrotreating reactor. Furthermore, itis contemplated that the portion of the hydrotreated feedstock in thevapor may vary considerably, and will, among other parameters, typicallydepend on the quality of the first and pressure conditions under whichthe hot separator is operated.

[0025] With respect to the composition of contemplated portions of thehydrotreated first feedstock in the vapor, it should be recognized thata particular composition of such portions will predominantly depend onthe particular composition and nature of the first feedstock. However,it is generally contemplated that preferred compositions contain atleast some material with a boiling point range that lies within theboiling point range of the second feedstock.

[0026] Dimensions and capacities of contemplated hydrotreating reactorswill typically depend at least in part on the particular feedstock, andthe overall throughput capacity of the hydrogenation plant. Thus, it iscontemplated that all known hydrotreating reactors are suitable for useherein. However, it is generally preferred that the hydrotreatingreactors will be operated under conditions that ensure hydrogenation ata relatively low level of hydrocracking (i.e., less than 15% conversion,more typically less than 10% conversion). Consequently, the nature ofthe catalyst may vary considerably. However, preferred hydrotreatingcatalysts will include those comprising cobalt, molybdenum and/or nickeldistributed on a carrier (e.g., alumina extrudate).

[0027] Furthermore, it should be recognized that by fluidly coupling thefirst hydrotreating reactor to the second hydrotreating reactor via thehot separator, the second reactor may be operating at a significantlyhigher pressure than a traditional standalone unit, which in turn willfurther reduce the amount of required catalyst for hydrotreating thesecond feed. It should be especially recognized that in preferredaspects of the inventive subject matter both hydrotreating reactors areoperated under conditions effective to reduce the concentration ofsulfur- and/or nitrogen-containing compounds in both feedstocks.Consequently, it should be recognized that in preferred configurationsboth feedstocks are substantially not (i.e., less than 10%, moretypically less than 8%) converted to lower boiling point products. Infurther particularly preferred aspects, the second feedstock comprisesdiesel, and the diesel contains after hydrotreating and columnseparation less than 50 ppm, more preferably less than 25 ppm, and mostpreferably less than 10 ppm sulfur-containing products.

[0028] First and second hydrotreating reactors will preferab allowhydrotreating of the feedstock with a particular catalyst withoutsignificant hydrocracking (i.e., with less than 15% conversion, and morepreferably less than 10% conversion). Consequently, preferredtemperatures will generally be in the range of about 500° F. to about800° F., and more preferably between about 550° F. to about 750° F.However, it should be recognized that depending on the particularfeedstock of the first and second reactors, the temperatures may varyaccordingly. With respect to the temperature regulation in the secondhydrotreater, it should be recognized that the temperature in the secondhydrotreating reactor may also be regulated by the amount of the secondfeedstock that is fed into the second reactor. Moreover, it should berecognized that the second hydrotreating reactor may be operated to arelatively large extent through the heat and pressure provided by thefirst hydrotreating reactor.

[0029] Similarly, the pressure of the first and second hydrotreatingreactors may vary considerably, and a particular pressure will be atleast in part determined by the particular feedstocks and catalystsemployed for the hydrogenations. However, it is generally contemplated(a) the operating pressure of the first hydrotreating reactor will beequal to or higher than the operating pressure of the secondhydrotreating reactor, and (b) that suitable pressures will generally bein the range of between about 1000 psi and 2400 psi. In furtherpreferred aspects of the inventive subject matter, it is contemplatedthat the operating pressure in the second reactor is between 0 and 300psi less, and more preferably between 0 and 150 psi less than theoperating pressure in the first reactor.

[0030] Moreover, it should be recognized that by integration of twohydrotreating reactors into contemplated configurations, costs forconstruction and operation of contemplated plants will be significantlyreduced. For example, it is contemplated that the cost for a hydrogenrecycle compressor in contemplated configurations will be substantiallylower than the cost for two independent recycle compressors. In yetanother contemplated aspect, it is contemplated that the requiredcapacity increase for the heat exchanger and cooler within the recycleloop will be moderate to insignificant.

[0031] It should also be appreciated that suitable configurations mayinclude additional hydrotreating reactors (i.e., a third reactor, afourth reactor, etc.) and of the additional reactors are fluidly coupledto an existing separator that receives the product of the existing orpreceding reactor. With respect to the components (e.g., piping,hydrotreating reactor, compressor, heat exchanger, etc.) in contemplatedconfigurations, it is contemplated that all known and commerciallyavailable components may be employed. Thus, contemplated configurationsmay be employed for production of two products having different boilingranges and different product specifications, wherein such configurationsmay be realized in a new plant as well as implemented as an upgrade toan existing plant. For example, an existing gas oil hydrotreaterupstream of a FCC unit may be upgraded to include a second reactor (orreactor section) for producing high quality low sulfur diesel fuel.

[0032] Consequently, a method of operating a plant may comprise a stepin which a first feedstock is hydrotreated in a first hydrotreatingreactor to produce a hydrotreated first feedstock. In another step, thehydrotreated first feedstock is fed into a hot separator that produces ahot hydrotreated liquid and a hot hydrotreated vapor that contains atleast a portion of the hydrotreated first feedstock. In a further step,at least a portion of the hot hydrotreated vapor is mixed with a secondfeedstock to form a mixed second feedstock, and in a still further step,the mixed second feedstock is fed into a second hydrotreating reactor toform a product, wherein the second feedstock has a boiling point rangethat is lower than the first feedstock. With respect to the first andsecond hydrotreating reactors, the hot separator, the feedstocks, andthe product, the same considerations as described above apply.

[0033] Thus, specific configurations and methods of combinedhydrotreating have been disclosed. It should be apparent, however, tothose skilled in the art that many more modifications besides thosealready described are possible without departing from the inventiveconcepts herein. The inventive subject matter, therefore, is not to berestricted except in the spirit of the appended claims. Moreover, ininterpreting both the specification and the claims, all terms should beinterpreted in the broadest possible manner consistent with the context.In particular, the terms “comprises” and “comprising” should beinterpreted as referring to elements, components, or steps in anon-exclusive manner, indicating that the referenced elements,components, or steps may be present, or utilized, or combined with otherelements, components, or steps that are not expressly referenced.

1. A plant comprising: a first hydrotreating reactor that receives afirst feedstock and produces a hydrotreated first feedstock; a hotseparator that receives the hydrotreated first feedstock and produces ahot hydrotreated liquid and a hot hydrotreated vapor that contains atleast a portion of the hydrotreated first feedstock; wherein at least aportion of the hot hydrotreated vapor is mixed with a second feedstockto form a mixed second feedstock that is fed into a second hydrotreatingreactor to form a product; and wherein the second feedstock has aboiling point range that is lower than a boiling point range of thefirst feedstock.
 2. The plant of claim 1 wherein the hot separator isoperated at a temperature of between about 450° F. and 550° F.
 3. Theplant of claim 2 wherein the hot separator is operated at a pressure ofbetween about 1200 psi and about 2400 psi.
 4. The plant of claim 1wherein the first hydrotreating reactor operates at a first pressure andthe second hydrotreating reactor operates at a second pressure, andwherein the second pressure is between 0 and 300 psi less than the firstpressure.
 5. The plant of claim 4 wherein the first pressure is apressure between about 1000 psi and 2400 psi.
 6. The plant of claim 1wherein the first feedstock comprises gas oil.
 7. The plant of claim 6wherein the second feedstock comprises diesel oil.
 8. The plant of claim7 wherein the first feedstock and the second feedstock have a ratio ofbetween about 1:1 to about 1:2.
 9. The plant of claim 1 wherein the atleast one of the first and second hydrotreating reactors further receivea hydrogen-containing stream.
 10. The plant of claim 9 wherein at leasta portion of the hydrogen-containing stream is recycled in the plantfrom an effluent of the second hydrotreating reactor.
 11. The plant ofclaim 9 wherein at least a portion of the hydrogen rich stream is amakeup hydrogen stream.
 12. The plant of claim 1 wherein the hotseparator and the second hydrotreating reactor are integrated as anupgrade into an existing hydrotreating plant.
 13. A method ofhydrotreating comprising: hydrotreating a first feedstock in a firsthydrotreating reactor to produce a hydrotreated first feedstock; feedingthe hydrotreated first feedstock into a hot separator that produces ahot hydrotreated liquid and a hot hydrotreated vapor that contains atleast a portion of the hydrotreated first feedstock; mixing at least aportion of the hot hydrotreated vapor with a second feedstock to form amixed second feedstock; and feeding the mixed second feedstock into asecond hydrotreating reactor to form a product, wherein the secondfeedstock has a boiling point range that is lower than a boiling pointrange of the first feedstock.
 14. The method of claim 13 wherein thefirst feedstock comprises gas oil and wherein the second feedstockcomprises diesel.
 15. The method of claim 13 wherein the hot separatoris operated at a temperature of between about 450° F. and 550° F. and apressure of between about 1200 psi and about 2400 psi.
 16. The method ofclaim 15 wherein the fist hydrotreating reactor operates at a firstpressure and the second hydrotreating reactor operates at a secondpressure, and wherein the second pressure is between 0 and 300 psi lessthan the first pressure.
 17. The method of claim 16 wherein the firstpressure is a pressure between about 1000 psi and 2400 psi.
 18. Themethod of claim 13 wherein the first feedstock and the second feedstockhave a ratio of between about 1:1 to about 1:2.
 19. The method of claim13 wherein the hot separator and the second hydrotreating reactor areintegrated as an upgrade into an existing hydrotreating plant.